Method for regulating the power output of a hot gas engine

ABSTRACT

Power output of a Stirling type hot gas engine is regulated by a valve control of the flow into a dead volume chamber connected to a low temperature working gas portion of a cylinder. The valve is operated to initially fully open the dead volume chamber and then to partially close over a continuously decreasing condition to a limiting position such that the power is minimized at maximum permissible engine speed, thereby preventing runaway speeds.

United States Patent [1 1 Jansson Jan. 14, 1975 METHOD FOR REGULATING THE POWER OUTPUT OF A HOT GAS ENGINE [75] Inventor: Lennart Ingemar Jansson,

Karrsangarvagen, Sweden [73] Assignee: Kommanditbolaget United Stirling (Sweden) AB & C0., Malmo, Sweden [22] Filed: Aug. 22, 1973 [21] Appl. No.: 390,622

[30] Foreign Application Priority Data Aug. 22, 1972 Great Britain 38970/72 [52] US. Cl. 60/521 [51] Int. Cl. FOZg 1/06 [58] Field of Search 60/521, 522

[56] References Cited UNITED STATES PATENTS Rinia et a1. 60/521 Kohler 60/521 Meyer 60/521 Primary ExaminerMartin P. Schwadron Assistant Examiner-ll. Burks, Sr.. Attorney, Agent, or FirmLaurerice R. Brown [57] ABSTRACT Power output of a Stirling type hot gas engine is regulated by a valve control of the flow into a dead volume chamber connected to a low temperature working gas portion of a cylinder. The valve is operated to initially fully open the dead volume chamber and then to partially close over a continuously decreasing condition to a limiting position such that the power is minimized at maximum permissible engine speed, thereby preventing runaway speeds.

3 Claims, 3 Drawing Figures METHOD FOR REGULATING THE POWER OUTPUT OF A HOT GAS ENGINE This invention relates to a method of regulating the power output of a hot gas engine by connecting the working gas spaces to dead volume chambers through channels having adjustable resistance against gas flow.

FIG. 1 is a graph in which the ordinates represent torques and the abscissa represents the opening towards the dead volume chambers.

FIG. 2 is a schematic of one cylinder of a hot gas engine.

FIG. 3 is a schematic diagram of a valve member as shown at 11 in FIG. 2.

The torque of a hot gas engine running at a constant speed will decrease if the working gas spaces are connected to dead volume chambers. If the connections do not offer any substantial resistance against gas flow the efficiency of the engine is not affected. However, if the connections do offer such resistance the efficiency may be lowered to such an extent that the power output is negative, i.e., the engine will function as a brake relative to its load. Such an effect is illustrated in FIG. 1 of the accompanying drawing, which is a graph in which the ordinates represent torques and the abscissa represent the openings towards the dead volume chambers. Three curves are shown, corresponding to minimum speed (dotted line of curve A) a medium speed (full line of curve B) and maximum speed (dash-dotted line of curve C).

FIG. 2 of the said drawing shows schematically a part of a hot gas engine having a cylinder 1 receiving a pis ton 2 connected to a piston rod 3 which in turn is connected to a crank-shaft (not shown). The working space in the cylinder 1 below the piston 2 is connected to a cooler 4 and a regenerator 5 through a pipe 6. The top of the regenerator 5 is connected to the heater at the top of another cylinder (not shown) through a pipe 7. The top of the cylinder 1 is connected to the top of another regenerator (not shown) through a pipe 8 acting as a heater.

The working space of the cylinder 1 below the piston 2 is also connected to a dead volume chamber 9 through a channel 10 containing a valve 11. This valve may be of any suitable known type, but its function should be that of the valve illustrated schematically in FIG. 3.

The valve of FIG. 3 comprises a valve member 12 fastened to a valve stem 13 provided with a roller 14 actuated by a cam 15. If the cam 15 is moved towards the right the valve member 12 will suddenly become moved to its fully opened position. A further movement of the cam towards the right will cause a gradual closing of the valve, causing an increase in resistance against gas flow. However, the valve will not become closed to an extent exceeding that corresponding to the value 0 (shown in FIG. 1).

According to the invention there is employed a method of regulating the power output of a hot gas engine by connecting the working gas spaces to dead vol ume chambers through channels having adjustable resistance against gas flow, characterised in that opening of the channels to the dead volume chambers is initiated by establishing a non-throttled passage and that subsequent throttling of said channels is only possible continuously to such degree as will cause minimum power output at the predetermined maximum permissi ble speed of the engine.

In this way it is possible to avoid operating within the ranges corresponding to the torque curves to the left of the value 0 of FIG. 1. It will be understood that during operation in such ranges an increase of engine output would cause increase in speed which would cause a further increase in torque resulting in a further increase in speed, with risk of the speed becoming excessive.

What is claimed is:

1. A valve connected for controlling the dead volume of the low temperature working gas space in a hot gas engine to regulate the power output comprising in com bination, a dead volume chamber connected to said low temperature working gas space by valve structure for controlling flow of gas between said chamber and said space, and means operating said valve structure for varying the flow of gas through said valve in a flow pattern passing from an initial maximum gas flow condi tion through a gradual decrease of gas flow.

2. A valve as defined in claim I wherein the gradual decreasee of gas flow is limited to that value causing minimum power output at the predetermined maximum permissible speed of the engine.

3. A valve as defined in claim 1 including structure that prevents closing said valve to prevent flow of gas therethrough. 

1. A valve connected for controlling the dead volume of the low temperature working gas space in a hot gas engine to regulate the power output comprising in combination, a dead volume chamber connected to said low temperature working gas space by valve structure for controlling flow of gas between said chamber and said space, and means operating said valve structure for varying the flow of gas through said valve in a flow pattern passing from an initial maximum gas flow condition through a gradual decrease of gas flow.
 2. A valve as defined in claim 1 wherein the gradual decreasee of gas flow is limited to that value causing minimum power output at the predetermined maximum permissible speed of the engine.
 3. A valve as defined in claim 1 including structure that prevents closing said valve to prevent flow of gas therethrough. 